The fragile X syndrome is the most common inherited form of mental retardation known. It also causes learning disabilities in carrier females and higher functioning males. It is relatively common, causing mental retardation in approximately 1 per 1200 in the general population. Significant advances in the molecular field including the utilization of PCR technology, molecular clinical correlations, characterization of the fine structure of the FMR-1 gene and protein function studies, are dramatically changing methods of diagnosis, genetic counseling and our understanding of the clinical spectrum of involvement from this disorder. These issues will all be addressed at the Fourth International Fragile X Conference, June 8-12, 1994 in Albuquerque, New Mexico. We are seeking funding from NIH to support the travel and lodging of an international faculty to present their latest research and to plan for future directions in the field. The emergence of screening studies utilizing new molecular technology has stimulated ethical debates which will be addressed in this conference. In addition, as a larger number of patients are identified, many professionals in schools, private practice, and in institutions who are treating fragile X patients are in need of information regarding the most optimal intervention possible. A view of the future will include a discussion of protein replacement studies and gene therapy. We are also seeking funding to allow young investigators to attend this conference and present their research. In addition, a conference proceedings will be published within 6 months of the conference and disseminated through the national and international network of resource centers associated with the National Fragile X Foundation. The International Fragile X Conference will focus on three areas of interest: the advances in molecular biology, treatment issues, and screening studies which include ethical issues. Expert speakers will be brought in from international centers and across the United States to 1) educate parents and professionals about recent advances, 2) provide a forum to standardize diagnosis, evaluation and counseling techniques, and 3) stimulate further research and international collaboration.